Member postings for Ajohnw

Some one mentioned a different test for the power piston earlier Brian. Drops though and doesn't with a finger on the end of the cylinder. If it was pressed when a finger is on the end sealing of the chamber there should be some springiness / resistance. A bit like an air bearing - a tough thing to make at that level.

A pop test without knowing exactly what it is sounds like the piston is pulled out with the end cover on - that may well pop if it's pulled out fast enough.

Ian's reamer might give you the sort of hole tolerance that Geoff mentions which in practice is more or less the same as a decent reamer. One thing I find odd about reamers these days is that if I measure one rather than being exactly on size they tend to be mid way in the tolerance band. The advantage of Ian's reamer is that it could be tried on a piece of scrap and polished down a touch if needed - it would have to be by rather minute amounts. Bigger D bits tend to produce holes up to 1 1/2 thou over their size, more or less twice what a reamer tends to give.

John

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Sounds like my guesstimate was about right Mike.

The 22 rimfire target rifles were only cleaned now and again. Basically not very often. A specific person who belonged to the club used to decide when and did it.

Talking rifles my admiration goes to the people most have seen shooting in Zulu. I was talking to some one at the club about the rifles used and he promptly fetched one and asked if I'd like to try it. Next week though so he could load some rounds. Having tried it I can well understand why they always seemed to be shot standing and not prone though that could be done with some care. He generally only part loaded them but did a dozen full for me, with a smile in his face. The kick is horrendous. The only rifle i have shot that was worse used to be used by a few for elephant hunting etc. The charge and slug was reckoned to be as much as the human frame could realistically stand. The zulu style riffles were nearly a bad. I like martini action for single shot but it's thin on the ground.

Old muskets are interesting too. I tried one once and got cheer plus a round of applause when I leaned into it to control the kick. It hurt. They are way more powerful than I suspect most people think.

I also tried to use a winchester john wayne style. They wont load quick enough. A certain copy will though.

John

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I didn't know those came with a T slotted cross slide Neil. Surely you didn't make it on it via a Taig vertical slide.

John

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Pultra 1750, 1770. Adding to Michaels post a little. Not exactly problems just factors.

The headstock bearings look like they are easily adjustable via nuts on each end. In practice these close the bearing down hard onto a laminated shim.

Makes adjustment interesting as there will be some wear on the spindle so I suspect it was a case of remove the lot, remove a shim, clamp it all up and adjust hole size to suit the spindle, Take apart again and re assemble.

There are variations.

Some have a thrust race to take up spindle end float. Others have a sleeve instead and the spindle has to be adjusted so that this runs up against the ends of one of the bearings. I suspect this type is the one that was cleared for 10,000 rpm use.

Some may have conventional gib strips on the slides rather than the taper adjusted type.

Some 1770's use a 1750 head fitted onto a suitable riser block. Going on the ones I have seen these will have the thrust race and the taper gib strips. Suspect both are down to S&B.

It's possible to move the cross slide well out from the bed for large swings and fit the normal riser blocks to both models which pushes the centre height well up - I'd guess this is how things get broken. I don't think that the lathe is suitable for anything other than extremely light work when it's use like this.

They used to make attachments for these machines on request. I suspect that if some one asked for something along the line of screw cutting, chasers or via gears they would mount it on the nicely machined flange under the end cover. That might explain why there are so many tapped holes in it. Might make a nice project for some one with one.

John

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I installed one of the usual Venetian blind types that just swing out when the extractor is on. On an exposed wall in West Wales. No problems with significant cold air coming in but sometime when it's rather windy with high gusts and it does get really windy there the blinds move and make the odd near bang type noise from time to time. Not often enough to be annoying. It does shut correctly The property is only a mile or so from the coast, less from a rather large estuary.

It's much like this one but the slats may be more recessed. Hard to tell from the photo

**LINK**

John

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Edited By Ajohnw on 20/02/2016 16:09:37

My feeling is that a toolmakers reamer will produce a hole with more clearance than the same sized real reamer much like D bits do. I've only used a D bit on brass and at a much larger diameter.

Exact size silver steel - I did know of one source that was exact as the company that was selling it had it made in a few sizes specifically for one of their customers.

The marine shafting linked to is very close tolerance but what about the hole ? I still think you would be better off reducing 1/8 dia to fit maybe plus a bit of lapping. You wont need your tailstock for that.

I don't know if you have tried a smaller more localised flame but it is possible to put too much heat in these things. The temperature differential has to be maintained for them to work.

John

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Must admit I was rather surprised when some one posted a shot of the headstock bearing arrangement Colchester generally seem to use. I expected better a la cva and some other Brit lathes also Schaublin. Plain bearings can be be better but wear is more of a problem. The worst lathe I used in training was a Chipmaster. Spent most of it's time running at 3,000rpm doing small work and not all that much of it really. There is not much scope for taking bigger cuts to get rid of surface finish problems on small work. If lathes need to run that fast they really aught to change the types of bearings used at this sort of spindle size.

My father could probably have obtained a selected CVA for me cheaply. One aspect that worried me was the weight but the main one was the usual bits and pieces. The training one was fully equipped including coillets and a fancy screw cutting indicator that would also cope with metric. Gears for DP and Mod too.

Myford popularity is easy. A budget lathe and many years of mags showing all sorts of things that can be made on them - sometimes suffering as a result. I'm thinking of things like the College Engineering rotary table kit. Originally designed to be made on a Boxford or larger. Slimmed down to get in the myford gap. For me a Raglan is a much better machine with that style of bed and cheaper used too. I think all of those have hardened bed guides but may be wrong. The make died when Myford bought them out. They even have variable speed without messing with inverters. They can be reconditioned as well but the unworn part of the rails which are fastened to the bed needs clocking up extremely precisely and it would probably pay to have the underside of the saddle licked over as well. The cross slide on mine was fine. The actual bed wear it had wouldn't bother most people but I don't have a cylindrical grinder. The attitude comes from using certain lathes in the past. I can't get rid of it.

Most milling during training was horizontal, things like V blocks, rather large twist drills, gears and other bits and pieces. I did use a 12" face cutter on a very hefty turret miller and a few jobs like that but better results would have been obtainable horizontally on the right machine. It was 2 long heavy V rails for a machine. They went on to be ground anyway.

I have used a Bridgeport in my own time at work. My impression was a bit light weight for the table size but capable. I suspect fame came from various gizmo's. This one was fitted with optical scales, viewed not digital so people could use it as a down market jig borer / set very precisely. In a small workshop along with various welding set ups a decent pillar drill and a Harrison like lathe. None of it used that much. I can't remember the makes of some of the lathes that I have used but this one had the essentials, bed guides nice and long and could pass either side of the headstock and tailstock. Nice long head - good for alignment, whisper quiet gear head and a sensible range of feeds. Wear wise it was at point where a certain depth of cut and feed rate combination was needed for best finish so would probably be turning a bit of a taper. Some one made a snooker cue on it by offsetting the tailstock. Afterwards it was low by about 1/32 or so. I'd guess the some one lost some shims but he reckoned not, It was smack on before that as far as I could tell.

I wish I had space to set my small shaper up - a very under rated type of machine when people aren't in a rush. The equivalent of a lathe in some ways but for flat work. It can be extremely flat too.

John

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No where is probably the answer to that Brian. Your best bet would be to buy 1/8" dia an very carefully polish it down. When it fits but is a bit stiff the best option would probably be to lap the two together with silvo/brasso etc but the diameter along the bar will have to be VERY consistent.

Then if you reamed in the lathe using a lubricant and at a slow speed immediately after drilling the hole things should work out. If I remember correctly from when Hopper was working on it your tailstock alignment is good. If not the reamer will produce a hole that is larger than it should be.

Only problem is that 1/8 dia might just turn out to be 50u bigger than 3mm. Stainless is usually a couple of thou down so that would leave it circa 100u over size.

Edit. There is an old trick for polishing bar I just remember and haven't actually tried. Books usually mention lead laps but it's possible to make them out of wood, pref a hard wood. 2 hinged pieces. Space the business end in this case say with 1 or 2 thickness's of photo copy paper. Drill a 1/8" hole centred on the gap, rub some lapping paste into it and then use it on the bar in the lathe moving it rapidly back an forth using finger pressure to to press it onto the work. At this sort of size there would be no need for the hinge really.

The same sort of thing can be done on holes using a dowel with a split in the end. There is a video  of this being done on rifle barrels by people dressed in ancient clothes. I reckon they have it wrong though, pushing the lap through rather than pulling but maybe the Brits made better rifle barrels. In this case, make the split etc and turn it to a suitable size then use.

John

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Edited By Ajohnw on 20/02/2016 11:05:39

My training was like that Nigel, but one mistake and no more progression. That's how a place can finish up with something like a Lang Toolroom lathe that's been there for some time yet only had days of light work done on it. I had a bit of 1/2 bar to turn up to something on that one. It took a few hours. Initial work was things for the toolbox. That was used to sort people then odd ball more interesting jobs passed on from the factories.

Officially I didn't get to use the CVA. I had a name for being heavy on machine tools if needed and they were worried I might spoil it. Fat chance within reason. My father loved them. He had a room set up with 1/2 dozen of them in it for production use when needed. Making obsolete car parts. Precise, long lasting and a small footprint. Even these get worn well past anything resembling precision as they all do eventually. I suppose luck might turn things up from time to time but lathes and other machines tend to have the jobs that are done on them changed as they wear.

In real life many things made in toolrooms are hardened and if precision is needed anyway the work finishes up on grinders. So much for my training but it all changed not long after I finished.

Really the slightly worn and worse ones are in some ways they ones that need most skill to get the best out of them. But " slight and worse limits what they can do without further corrections. Super duppa stuff all comes down to how tools are ground and speeds and feeds. That area is why I have no respect at all for the usual tables. Even the lathes themselves vary.

John

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I can't see how anyone can rate a lathe unless they have used lathes in this sort of condition and also ones at various states of wear. I have. The Lang and also a DSG with toolroom in the name are probably pretty rare but I have also used a lot of other brands in various states of wear and with what might be called initial states of quality.

Not boasting or anything else like that but when people say they have a wonderful this or that I wonder how they know it's wonderful or even what they mean in practice when they state that sort if thing,

Just curious really because I know there is zero chance of me having a lathe at home that is anything like some I have used. Probably not even a Student as like many wear shows in a surprisingly short time when they are really used.

There are some things that irritate me performance wise about my Boxford but no point in mentioning them really as it's a Boxford. A brand new one might resolve these irritation or more likely some of the new ones might but that state of affairs wouldn't last long. The same is true of many lathes even bigger ones.

John

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I have a GAST that was used with a Badger. The compressor head take a male thread 0.5145 dia so 1/4 bsp. Same in and out.

It has a sticker on it that says £15 - did I do well. It's fine.

John

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Looks like back to 2012. Really they should be able to offer everything since digital which aught to be well before that. Maybe even back to the late 70's.

Personally particularly with ME I often find the very old ones most interesting.

John

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Hacksaw mentioned the usual way of doing it simply. When I used the rack feed on a Raglan to slot a bore 2 failed after the last cut. They pegs were silver steel, 2 across the gear. The ones that were left meshed well suggesting that they had been cut properly. It was a fairly coarse gear.

The other way is to slot and fit and fix a piece of metal in and recut the tooth. Don't let it cool too quickly if the piece is braised in.

Personally as you have a gear with the correct tooth count best make a new gear.

John

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Hands up.

Who on here have used say for instance a Lang Toolroom or a Colchester Student that hasn't had many hours of even light work done on it. Say 2 weeks max and by no way continuous and oiled well each week even if it's not been used.

Anything similar would do. Very top end such as the Lang and middling such as the Student. Or anything in between.

John

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The design is probably basically correct so should work as is. It might be worth moving the displacer back away from the end of the tube if that is getting to hot.

They are curious things. The regenerator should be hotter at one end than the other, just like the displacer. The idea of the regenerator is to heat the cold air as it passes through it. I'm inclined to say really ????? but some sort of balance must be achievable.

This is a low temperature one and the gap around the displacer is very visible. It's made using stuff from Lidl.

Annoying. I had been wondering if they could be made like this - no power piston as such, just a piece of light rubber. Somebody now has done it. NASA seem to use a similar set up with what are referred to as free pistons. No con rod.

I keep meaning to make a bit of an extension on my Boxford Bob. Trouble with swarf coming out of the front is it gets in the chuck. The boxfords have tubular extension that goes over the spindle end built into the change wheel cover but sometimes it still gets in.

John

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Backlash is dealt with by accounting for it when the tool position is changed. Say it needs moving out by some amount. Note reading, move out that distance plus backlash plus some more and then wind in to the correct reading.

The plus some more needs to be several times the amount of backlash. Often a near full turn is convenient - and a good idea for accurate work.

So called jam nuts used to adjust it out are a bit of a joke long term.

John

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LOL I don't think life in terms of how much time the bullet spends travelling down the barrel is practical at all. I'd me more concerned about how often I would have to buy a new one.

John

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I've seen some fairly old full bore (nato 7.62mm) target rifles being used that were still clearly pretty accurate - only variation due to cross wind when conditions are like that. They start at 300m and then go longer.

The barrels do get changed as some point but as they are generally only used for competition shooting I'd guess 10 to 15 years as there are only so many ranges, some will be too far away for people to travel so I doubt if they are shot every month. This sort of shooting allows 2 sighters before the ones that count are shot. So going on that some where in the region of 1500 rounds plus or minus ??. That;s assuming 300 and 600 are shot every time. Some ranges do another longer distance as well. That might push it up to 2000 rounds.

John

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If I remember correctly some / all Zyto's were made in Germany to save money and equipped with a change wheel cover marked made in good old GB, that part was.

John

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